EpsilonTensor product not showing negative sign?

Question

Need help with the following code. Trying to show

$\epsilon^{iklm} \epsilon_{prlm} = - 2( \delta_p^i \delta^k_r - \delta^i_r \delta^k_p ) $

Tried the following code:

yields $2( \delta_p^i \delta^k_r - \delta^i_r \delta^k_p )$ without negative sign!

{i,k ,l,m,p,r}::Indices.
{i,k,l,m,p,r}::Integer(1..4).
\delta{#}::KroneckerDelta.
\epsilon^{i k l m}::EpsilonTensor(delta = \delta);

eq3 := \epsilon^{i k l m} \epsilon_{p r l m};
epsilon_to_delta(_);
expand_delta(_);

enter code here

Answer 1

Cadabra's epsilon product will always produce a plus sign, irrespective of the signature of the metric. So you'll need to stick in that '-1' by hand if your convention is different.